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beachbum

ok guys whats wrong with my brat???

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1985 brat 1.8 runs perfect in traffic at lights runs good and cool,if i turn on my a/c it goes right up to hot the highest point?timing is dead on never loses any fluids,tranny or otherwise,fans r all working and spinning fast,i can drive it all day around town and it stays cool,but as soon as i turn on the a/c it gets hot to the point the valves will start clanging,and as soon as i shut off the a/c goes back to cool and no valve noise,i just had the heads done about three months ago,and as i said the timing is right on,fans r working. what else can i check? or what is causing this? thnx for any and all help as usual.. beachbum

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Does the A/C work correctly? Have you checked all the belts? All I can think of off the top of my head is that once the A/C comes on, the water pump is no longer being turned, causing the overheat.

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Does the fan run when the A/c is on? Why do you have AC anyway =P?

 

MAKE SURE THE FAN CYCLES!Replace the thermostat, check for colapsed hoses,

If it has a fanclutch replace it if it spins freely.

 

Lug it up a steep hill, does it heat up?

 

Flo test the radiator.

 

If you do all that and it still heats up do the head gaskets.

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Pull the radiator and inspect it. Sometimes the cooling fins get bent or fall apart with age. Once you get the raditor out, rinse it with a hose to see how loose the fins are. I doubt its head gaskets, it sound more like a radiator issue. Dont bother getting the radiaotr rebuilt, just get another one off the net.

 

nipper

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ok guys, yes the a/c works and the 2 fans are electric and work well.the water in the radiator is circulating well with the a/c on or off, the belts are fine and everything is turning as it should.i just had the heads redone about three months ago and new gaskets put on then.. under any load in this heat the truck never gets hot until the a/c is on?i havent replaced the thermostat yet cause i figured if it didnt get hot otherwise it was ok.but i will and ill clean the radiator but as i said a second ago,it runs fine and cool until the a/c is on..but ill try the 3 suggestions u gave me and ill let u know in a couple of daz if it help. thnx again beachbum oh and to answer an earlier question(why do i have a/c anyway) this is florida man its freaking hot here.93 today :grin:

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Sounds like it is time to go through the wire harness.......

 

Looks like you've checked for a locked compressor and fan malfunction.........

 

Unless there is trash trapped between the condenser and radiator(I've had this happen, but not on a sube), this may be your fix, outside of adding a seperate temp. gauge....

 

Don

Pictzie

'92Loyal 2wd

'93Loyal 4X4(my fiancee's)

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Probably time for a new radiator - most likely the only part of the radiator that is still working is the section immediatly behind the AC evaporator, as that section is protected from debris. Once the AC is turned on, the evap gets hot, and the heat flowing directly into the radiator from it overcomes the cooling system. Probably bent fins and debris and partial blockage of your radiator are to blame. Easiest way to check is get one of those laser temp guages and check the temp at various places on the radiator suface. This will tell you where coolant is flowing, and where it is not. But everything else being as you say, it's almost certainly the radiator that is at fault as that is the only point where the AC system and the coolant system are in close proximity.

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i bought a new-er radiator today and took it down to have tested and cleaned and got me a new thermostat,will get them in this wknd. and let u guys know thnx bb

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